The technical and commercial threats posed by solids (sand) and the corrosivity of fluids produced from the reservoir formation are well known to oil and gas operating companies and asset managers. Proactive strategies are required to manage the impact of these solids and corrosive fluids on production and to maximise productivity. Solids production is typically episodic and can cause extreme damage almost instantaneously. Corrosive fluids can also be episodic due to water breakthrough. The consequences can include reservoir damage, erosion of choke valves, erosion and accelerated corrosion of pipework, reduction of corrosion inhibitor performance and the filling of Separators: all resulting in reduced productivity. Reliable instantaneous management of solids in offshore and subsea systems is of vital importance.
At present a number of independent discrete sensors are used to monitor corrosion, erosion and sand individually in oil and gas pipelines. The various sensors are often provided by different manufacturers, and the measurements taken by different sensors are not easily correlated. Relevant prior art is described in U.S. Pat. No. 6,946,855 (Hemblade), U.S. Pat. No. 7,878,047 (Hemblade) and US Patent Publication No. 2010/0326654 (Hemblade).
In U.S. Pat. No. 6,946,855, an apparatus is disclosed for monitoring the effect on a material of exposure to a fluid, and thereby monitoring the effect on a section of pipe for carrying the fluid. The apparatus includes a sensor element exposed to the fluid and formed as a ring of the material coaxially mounted within, but electrically insulated from, the section of pipe. Changes in the electrical resistance of the sensor element are monitored. Preferably, the apparatus also includes a reference element electrically insulated from the pipe, electrically connected in series to the sensor element and protected from exposure to the fluid. The elements may both be made from the same material as the pipe and, as they are contained within it, experience the same temperature and pressure variations as the pipe. In this manner a change in the resistance of the sensor element caused by corrosion/erosion by the fluid accurately indicates the degree of corrosion/erosion of the pipe carrying the fluid.
In U.S. Pat. No. 7,878,047, there is described an apparatus for monitoring particles in a fluid stream, comprising a body portion and a detector element that is acoustically decoupled from the body portion. The detector element comprises a target surface, a sample acoustic sensor and a corrosion sensor. The sample acoustic sensor is acoustically coupled to the target surface and is arranged to provide a first signal, which varies in dependence upon acoustic noise generated by impacts of particles and fluid on the target surface. The corrosion sensor is arranged to provide a second signal, which varies in dependence upon corrosion and/or erosion of the target surface. A corresponding method of monitoring particles in a fluid stream is also described. The method and apparatus are suitable for monitoring sand in oil and gas production flow streams.
In US Patent Publication No. 2010/0326654, an apparatus monitors a production flow from a gravel pack into a tubular sand screen disposed concentrically around downhole production tubing in an oil or gas well. A tubular sample layer is disposed concentrically around the sand screen to be exposed to the radial production flow in use. The sample layer is electrically insulated from the production tubing in use. An erosion sensor provides a signal which varies in dependence upon an electrical resistance of the sample layer, which is related to the erosion of the sample layer. An apparatus also monitors a substantially longitudinal production flow through downhole production tubing in an oil or gas well. A method and apparatus are used to monitor the condition of a gravel pack within an oil or gas well. Other methods monitor temperature or pressure conditions within an oil or gas well.
There is a need for tools for the corrosion management of produced fluids, sand management prediction and quantification, integrated modelling and chemical optimisation.
The present invention seeks to provide an improved apparatus for characterising a flow through a conduit which provides various advantages over those of the prior art, including reduced capital expenditure opportunities and improved correlation and performance for the operator. In addition, the present invention aims to improve characterisation of the hydrocarbon production stream in terms of asset integrity and flow assurance in order to enable operators to accelerate production, extend asset life, reduce intervention costs.